(7/25/13 6:25 PM), Johannes Weiner wrote: > System calls and kernel faults (uaccess, gup) can handle an out of > memory situation gracefully and just return -ENOMEM. > > Enable the memcg OOM killer only for user faults, where it's really > the only option available. > > Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx> > --- > include/linux/memcontrol.h | 23 +++++++++++++++++++++++ > include/linux/sched.h | 3 +++ > mm/filemap.c | 11 ++++++++++- > mm/memcontrol.c | 2 +- > mm/memory.c | 40 ++++++++++++++++++++++++++++++---------- > 5 files changed, 67 insertions(+), 12 deletions(-) > > diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h > index 7b4d9d7..9bb5eeb 100644 > --- a/include/linux/memcontrol.h > +++ b/include/linux/memcontrol.h > @@ -125,6 +125,24 @@ extern void mem_cgroup_print_oom_info(struct mem_cgroup *memcg, > extern void mem_cgroup_replace_page_cache(struct page *oldpage, > struct page *newpage); > > +/** > + * mem_cgroup_xchg_may_oom - toggle the memcg OOM killer for a task > + * @p: task > + * @new: true to enable, false to disable > + * > + * Toggle whether a failed memcg charge should invoke the OOM killer > + * or just return -ENOMEM. Returns the previous toggle state. > + */ > +static inline bool mem_cgroup_xchg_may_oom(struct task_struct *p, bool new) > +{ > + bool old; > + > + old = p->memcg_oom.may_oom; > + p->memcg_oom.may_oom = new; > + > + return old; > +} The name of xchg strongly suggest the function use compare-swap op. So, it seems misleading name. I suggest just use "set_*" or something else. In linux kernel, many setter functions already return old value. Don't mind. > diff --git a/include/linux/sched.h b/include/linux/sched.h > index fc09d21..4b3effc 100644 > --- a/include/linux/sched.h > +++ b/include/linux/sched.h > @@ -1398,6 +1398,9 @@ struct task_struct { > unsigned long memsw_nr_pages; /* uncharged mem+swap usage */ > } memcg_batch; > unsigned int memcg_kmem_skip_account; > + struct memcg_oom_info { > + unsigned int may_oom:1; > + } memcg_oom; This ":1" makes slower but doesn't diet any memory space, right? I suggest to use bool. If anybody need to diet in future, he may change it to bit field. That's ok, let's stop too early and questionable micro optimization. > diff --git a/mm/filemap.c b/mm/filemap.c > index a6981fe..2932810 100644 > --- a/mm/filemap.c > +++ b/mm/filemap.c > @@ -1617,6 +1617,7 @@ int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf) > struct file_ra_state *ra = &file->f_ra; > struct inode *inode = mapping->host; > pgoff_t offset = vmf->pgoff; > + unsigned int may_oom; Why don't you use bool? your mem_cgroup_xchg_may_oom() uses bool and it seems cleaner more. > @@ -1626,7 +1627,11 @@ int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf) > return VM_FAULT_SIGBUS; > > /* > - * Do we have something in the page cache already? > + * Do we have something in the page cache already? Either > + * way, try readahead, but disable the memcg OOM killer for it > + * as readahead is optional and no errors are propagated up > + * the fault stack. The OOM killer is enabled while trying to > + * instantiate the faulting page individually below. > */ > page = find_get_page(mapping, offset); > if (likely(page) && !(vmf->flags & FAULT_FLAG_TRIED)) { > @@ -1634,10 +1639,14 @@ int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf) > * We found the page, so try async readahead before > * waiting for the lock. > */ > + may_oom = mem_cgroup_xchg_may_oom(current, 0); > do_async_mmap_readahead(vma, ra, file, page, offset); > + mem_cgroup_xchg_may_oom(current, may_oom); > } else if (!page) { > /* No page in the page cache at all */ > + may_oom = mem_cgroup_xchg_may_oom(current, 0); > do_sync_mmap_readahead(vma, ra, file, offset); > + mem_cgroup_xchg_may_oom(current, may_oom); > count_vm_event(PGMAJFAULT); > mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT); > ret = VM_FAULT_MAJOR; > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 00a7a66..30ae46a 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -2614,7 +2614,7 @@ static int mem_cgroup_do_charge(struct mem_cgroup *memcg, gfp_t gfp_mask, > return CHARGE_RETRY; > > /* If we don't need to call oom-killer at el, return immediately */ > - if (!oom_check) > + if (!oom_check || !current->memcg_oom.may_oom) > return CHARGE_NOMEM; > /* check OOM */ > if (!mem_cgroup_handle_oom(mem_over_limit, gfp_mask, get_order(csize))) > diff --git a/mm/memory.c b/mm/memory.c > index f2ab2a8..5ea7b47 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -3752,22 +3752,14 @@ unlock: > /* > * By the time we get here, we already hold the mm semaphore > */ > -int handle_mm_fault(struct mm_struct *mm, struct vm_area_struct *vma, > - unsigned long address, unsigned int flags) > +static int __handle_mm_fault(struct mm_struct *mm, struct vm_area_struct *vma, > + unsigned long address, unsigned int flags) > { > pgd_t *pgd; > pud_t *pud; > pmd_t *pmd; > pte_t *pte; > > - __set_current_state(TASK_RUNNING); > - > - count_vm_event(PGFAULT); > - mem_cgroup_count_vm_event(mm, PGFAULT); > - > - /* do counter updates before entering really critical section. */ > - check_sync_rss_stat(current); > - > if (unlikely(is_vm_hugetlb_page(vma))) > return hugetlb_fault(mm, vma, address, flags); > > @@ -3851,6 +3843,34 @@ retry: > return handle_pte_fault(mm, vma, address, pte, pmd, flags); > } > > +int handle_mm_fault(struct mm_struct *mm, struct vm_area_struct *vma, > + unsigned long address, unsigned int flags) > +{ > + int ret; > + > + __set_current_state(TASK_RUNNING); > + > + count_vm_event(PGFAULT); > + mem_cgroup_count_vm_event(mm, PGFAULT); > + > + /* do counter updates before entering really critical section. */ > + check_sync_rss_stat(current); > + > + /* > + * Enable the memcg OOM handling for faults triggered in user > + * space. Kernel faults are handled more gracefully. > + */ > + if (flags & FAULT_FLAG_USER) > + WARN_ON(mem_cgroup_xchg_may_oom(current, true) == true); Please don't assume WARN_ON never erase any code. I'm not surprised if embedded guys replace WARN_ON with nop in future. Thanks. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx"> email@xxxxxxxxx </a>